A Theoretical Study of Amine Bonding in Titanium Alkoxide Adducts

Summary. DFT calculations were carried out on Ti₂(OCH₃)₈ (NH₂CH₃)₂ and Ti₂(OCH₃)₈(NH₃)₂, which are model compounds for the previously isolated amine adducts Ti₂(OR)₈(NH₂ R′)₂. The calculations show that the Ti–N bond strength is weak; however, coordination of the amine to the metal center is supported by a N–H···O hydrogen bond of the amine with the neighboring alkoxo ligand. The Ti–N interaction is purely σ in nature, while the Ti–O interactions include both σ and π contributions. The lowest unoccupied molecular orbitals are mainly localized on Ti t_2g-like orbitals.     

Variation of interatomic distances in oxides

The average interatomic distances D in oxygen polyhedra MO _n of isostructural oxides were proposed to be estimated using the equation D = Kɛ(R _M + R _O) or D = Ax ² + Bx + C, where x = ɛ(R _M + R _O), ɛ is the ionicity of the M-O bond, R _M is the ionic radius of the cation M with account for the coordination in the polyhedron, and R _O is the ionic radius of oxygen. Calculations were made for MO oxides having the rock-salt structure; Ln₂O₃ oxides, where Ln = Ce-Yb; and the MO₂ oxides having the rutile and fluorite structures.     

Synthesis and Structure of Novel Dimethylcobalt(III) Complexes Containing Trimethylphosphine and Salicylaldiminato(N:O) Ligands

Dimethyl(salicylaldiminato[N:O])cobalt complexes [CoMe₂(2‐O‐C₆H₁R¹R² R³‐CH=NR⁴)L₂] (L=PMe₃) ( 1 ‐ 6 ) have been prepared through the reaction of [CoMe₃(PMe₃)₃] with the corresponding substituted salicylaldimine. The complexes were characterized with IR, ¹H NMR, ¹³C NMR, ³¹P NMR and elemental analyses. The X‐ray crystal structure of complex 1 shows an octahedral coordination of cobalt, with two equatorial cis‐methyl groups opposite to the planar N:O‐chelate ring.     

Hydrothermal synthesis, crystal structure and magnetic property of oxalate-bridged iron 1D chain coordination polymer

A novel oxalate-bridged iron coordination polymer, Fe₂(phen)₂(C₂O₄)₂ (1) has been hydrothermally synthesized and characterized by elemental analyses, IR spectrum, TGA-DTA analysis, and single-crystal X-ray diffraction. Compound (1) crystallizes in the monoclinic system, space group P2(1), the final R is 0.0486. The tetradentate-chelating coordination mode of oxalate anion creates an infinite 1D iron (II) oxalate chain structure and from which a 2D network is constructed by π–π interactions of phen rings. The temperature-dependent magnetic susceptibility measurement indicates the existence of a weak antiferromagnetic coupling between Fe^II ions.     

Synthesis and Reactivity of Stannyloligosilanes IV [1]: From Hydrido Substituted Stannasilanes Towards Stannasiloxanes

Summary.  Hydrido substituted stannasilanes of the type or (Z = H, Me, Ph; R, R′ = alkyl, Ph) are accessible by reaction of either alkali metal stannides (MSn(Z)R ₂; M = Li, Na) with halogen substituted silanes (; X = F, Cl) or chlorostannanes (R ₂SnCl₂, Ph₃SnCl) and fluorosilanes in the presence of magnesium. Stannasilanes with halogen substituents at the silicon as well as the tin atom are formed by treatment of the hydrido substituted stannasilanes with CHCl₃ or CCl₄. The hydrido substituted stannasilanes decompose in contact with air to distannanes and siloxanes or to the linear ( ^t Bu₂Sn(–O– ^t Bu₂Si–OH)₂) and cyclic ((– ^t Bu₂Sn–O– ⁱ Pr₂Si–O–)₂) stannasiloxanes. Received November 29, 2001. Accepted (revised) January 16, 2002     

Complexes of Zr<Superscript>IV</Superscript> and Hf<Superscript>IV</Superscript> with monolacunary Keggin-and Dawson-type anions

The reactions of the tetranuclear hydroxo complexes [M₄(μ₂-OH)₈(H₂O)₁₆]⁸⁺ (M = Zr or Hf) with the lacunary Keggin-type ([α-PW₁₁O₃₉]⁷⁻) and Dawson-type ([α ₂-P₂W₁₇O₆₁]¹⁰⁻) phosphotungstates in aqueous solutions produce the sandwich polyoxometalate complexes [M(α-PW₁₁O₃₉)₂]¹⁰⁻ (M = Zr (1) or Hf (2)) and [M(α ₂-P₂W₁₇O₆₁)₂]¹⁶⁻ (M = Zr (3) and Hf (4)). The complexes were isolated and structurally characterized as salts with potassium and dimethylammonium cations. The zirconium and hafnium atoms have a square antiprismatic coordination environment (coordination number is 8). In all complexes, the mutual arrangement of the ligands corresponds to the syn isomer. Hafnium complexes 2 and 4 are the first structurally characterized polyoxometalate complexes of this metal. The structures of the resulting compounds were confirmed also by ³¹P NMR spectroscopy in solution. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 214–218, February, 2007.     

Divalent transition metal complexes of 3,5-pyrazoledicarboxylate

New divalent transition metal 3,5-pyrazoledicarboxylate hydrates of empirical formula Mpz(COO)₂(H₂O)₂, where M=Mn, Co, Ni, Cu, Zn and Cd (pz(COO)₂=3,5-pyrazoledicarboxylate), metal hydrazine complexes of the type Mpz(COO)₂N₂H₄ where M=Co, Zn or Cd and Mpz(COO)₂nN₂H₄·H₂O, where n=1 for M=Ni and n=0.5 for M=Cu have been prepared and characterized by physico-chemical methods. Electronic spectroscopic data suggest that Co and Ni complexes adopt an octahedral geometry. The IR spectra confirm the presence of unidentate carboxylate anion (Δν=ν_asy(COO^–)–ν_sym(COO^–)>215 cm^–1) in all the complexes and bidentate bridging hydrazine (ν_N–N=985–950 cm^–1) in the metal hydrazine complexes. Both metal carboxylate and metal hydrazine carboxylate complexes undergo endothermic dehydration and/or dehydrazination followed by exothermic decomposition of organic moiety to give the respective metal oxides as the end products except manganese pyrazoledicarboxylate hydrate, which leaves manganese carbonate. X-ray powder diffraction patterns reveal that the metal carboxylate hydrates are isomorphous as are those of metal hydrazine complexes of cobalt, zinc and cadmium.     

Ionization potentials of non-metal monosulfides. Conjugation in radical cations containing Group IV elements

The first vertical ionization potentialsI(n_s) of 69 monosulfides XSY (X, Y=H, Hal, organic, or heteroorganic substituent) are related to the inductive σ_I resonance (σ _R ⁺ ) and polarizability (σ_α) constants of the substituents by dependences of theI(n_S)=a+bΣσ_I+bΣσ_R+bΣσ_α type. TheI(n_s) values are also affected by hyperconjugation which increases on going from XSH to XSY (Y≠H) compounds. The first calculations of the σ _R ⁺ parameters characterizing the conjugation of Si-, Ge-, Sn-, and Pb-containing substituents with the S^.+ radical cation center are reported. The reasons for weakening of resonance donor properties of heteroorganic substituents of the +M-type in the systems studied as compared to those of the same substituents in the corresponding aromatic radical cations are considered. Translated fromIzvestiya Akademii Nauk. Seriya Khmicheskaya, No. 1, pp. 25–31, January, 2000.     

Electrocatalytic activity and stability of Ti/IrO2 + MnO2 anode in 0.5 M NaCl solution

Ti/IrO₂(x) + MnO₂(1-x) anodes have been fabricated by thermal decomposition of a mixed H₂IrCl₆ and Mn(NO₃)₂ hydrosolvent. Cyclic voltammetry (CV) and polarization curve have been utilized to investigate the electrochemical behavior and electrocatalytic activity of Ti/IrO₂(x) + MnO₂(1-x) anodes in 0.5 M NaCl solution (pH = 2). Ti/IrO₂+MnO₂ anode with 70 mol% IrO₂ content has the maximum value of q*, indicating that Ti/IrO₂(0.7) + MnO₂(0.3) anode has the most excellent electrocatalytic activity for the synchronal evolution of Cl₂ and O₂ in dilute NaCl solution. Tafel lines displayed two distinct linear regions with one of the slope close to 62 mV dec⁻¹ in the low potential region and the other close to 295 mV dec⁻¹ in the high potential region. Electrochemical impedance spectroscopic is employed to investigate the impedance behavior of Ti/IrO₂(x) + MnO₂(1-x) anodes in 0.5 M NaCl solution. It is observed that as the R _ct, R _s and R _f values for Ti/IrO₂(0.7) + MnO₂(0.3) anode become smaller, electrocatalytic activity of Ti/IrO₂(0.7) + MnO₂(0.3) anode becomes better than that of other Ti/IrO₂ + MnO₂ anodes with different compositions. Ti/IrO₂(0.7) + MnO₂(0.3) anode fabricated at 400 °C has been observed to possess the highest service life of 225 h, whereas the accelerated life test is carried out under the anodic current of 2 A cm⁻² at the temperature of 50 °C in 0.5 M NaCl solution (pH = 2).     

Ionization potentials of non-metal monosulfides. Conjugation in radical cations containing Group IV elements

The first vertical ionization potentialsI(n_s) of 69 monosulfides XSY (X, Y=H, Hal, organic, or heteroorganic substituent) are related to the inductive σ_I resonance (σ _R ⁺ ) and polarizability (σ_α) constants of the substituents by dependences of theI(n_S)=a+bΣσ_I+bΣσ_R+bΣσ_α type. TheI(n_s) values are also affected by hyperconjugation which increases on going from XSH to XSY (Y≠H) compounds. The first calculations of the σ _R ⁺ parameters characterizing the conjugation of Si-, Ge-, Sn-, and Pb-containing substituents with the S^.+ radical cation center are reported. The reasons for weakening of resonance donor properties of heteroorganic substituents of the +M-type in the systems studied as compared to those of the same substituents in the corresponding aromatic radical cations are considered. Translated fromIzvestiya Akademii Nauk. Seriya Khmicheskaya, No. 1, pp. 25–31, January, 2000.     

Influence of the lead carboxylate on the molecular composition of its solutions with zirconium and titanium isopropoxides or n-butoxides: 2-ethylhexanoate vs acetate, a way to stabilize the first Pb-Zr carboxylatoalkoxides of 1:1 stoichiometry

The reactions between titanium or zirconium alkoxides namely Ti(OR)₄ (R = ⁱ Pr, ⁿ Bu) or Zr₂(O ⁱ Pr)₈(HO ⁱ Pr)₂, Zr(O ⁿ Bu)₄ respectively and lead 2-ethylhexanoate Pb(O₂CC₇H₁₅)₂ were investigated at room temperature (rt) and by heating. The various compounds were characterized by elemental analysis, FT-IR, ¹H and ²⁰⁷Pb NMR. The mixed-metal species obtained at rt were adducts Pb₄Zr₄(μ-O₂CR′)₈(OR)₁₆(OHR)₂ 1 and Pb₂Ti₄(μ-O₂CR′)₄(OR)₁₆ 2 (R′=CHCHEt(CH₂)₂Me, R = ⁱ Pr) independently of the stoichiometry used. The structures of 1 and 2 are based on triangular M₂Pb cores (M = Zr, Ti). with 6-coordinate transition metals -as required for perovskites- and 6- or 7-coordinate lead atoms. Similar observations were made with n-butoxides. Thermal and hydrolytic condensation reactions were investigated. Thermal condensation was more difficult for the n-butoxide derivatives than for the isopropoxide ones. Powders derived from the hydrolysis of the Single Source Precursor 1 in various conditions were characterized by TGA, XRD and SEM for the PZ ceramic.     

Oxo Peroxo Glycolato Complexesof Vanadium (V). Crystal Structureof (NBu4)2[V2O2(O2)2(C2H2O3)2]ċH2O

Summary.  Oxo peroxo glycolato complexes of vanadium(V) (M ₂[V₂O₂(O₂)₂(C₂H₂O₃)₂]ċnH₂O (n=0, 1; M=NBu₄ ⁺ (1), K⁺ (2), NH₄ ⁺ (3), Cs⁺ (4), NPr₄ ⁺ (5)) as well as (NBu₄)₂[V₂O₄(C₂H₂O₃)₂]ċ H₂O (6) have been prepared and characterized by spectroscopic methods. X-Ray structure analysis of 1 revealed the presence of dinuclear [V₂O₂(O₂)₂(C₂H₂O₃)₂]²⁻ anions with a (chemical structure) bridging core and six coordinated vanadium(V) atoms in a distorted pentagonal pyramidal array. Received July 12, 1999. Accepted (revised) October 28, 1999     

Kinetic of decomposition of some complexes under non-isothermal conditions

Kinetics of thermal decomposition of three structurally similar complexes Co₂Cu(C₂O₄)₃ (R-diam)₂, where R is ethyl, 1,2-propyl or 1,3-propyl, was studied under non-isothermal conditions and nitrogen dynamic atmosphere at heating rates of 5, 7, 10, 12 and 15 K min⁻¹. For data processing the Flynn-Wall-Ozawa and a modified non-parametric kinetic methods were used. By both methods the activation energy are in the range of 97–102 kJ mol⁻¹. The formal kinetic is r=kα(1−α)². Also a compensation effect between lnA and E was evidenced. The kinetic analysis lead to the conclusion of an identic decomposition mechanism by a single step process.     

Excitonic Bands in the Spectra of Some Organic-Inorganic Hybrid Compounds Based on Metal Halide Units

Summary.  The optical absorption, photoluminescence, and photoconductivity spectra of some compounds of the formulas [R(CH₂) _n NH₃] _x M _y X _z , [R(CH₂) _n NH(CH₃)₂] _x M _y X _z , [R(CH₂) _n S(CH₃)₂] _x M _y X _z , [R(CH₂) _n SC(NH₂)₂] _x M _y X _z , and [R(CH₂) _n SeC(NH₂)₂] _x M _y X _z (R = organic residue; M = Bi(III), Pb(II), Sn(II), Cu(I), Ag(I) etc; X = I, Br, Cl; n, x, y, z = 0, 1, 2, 3, …) are briefly reviewed, and some new results are reported. The position, intensity, and shape of the excitonic bands depend on the dimensionality and size of the inorganic network as well as on the nature of the M, X, R, and onium moieties. Received June 23, 2000. Accepted August 1, 2000     

IR and <Superscript>31</Superscript>P NMR spectroscopic study of complexation of carbamoyl methyl phosphinates with U<Superscript>VI</Superscript> and Th<Superscript>IV</Superscript> in nitric acid solutions

The composition of complexes formed upon the extraction of U^VI and Th^IV nitrates with O-n-nonyl(N,N-dibutylcarbamoylmethyl) methyl phosphinate (L) from solutions of nitric acid without additional solvent was determined by ³¹P NMR spectroscopy. The structures of the complexes formed were studied by IR spectroscopy. Uranium(VI) is extracted from 3 and 5 M solutions of HNO₃ as the [UO₂(L)₂(NO₃)₂] complex, while thorium(IV) is extracted from 5 M HNO₃ as the [Th(L)₃(NO₃)₃]⁺·NO ₃ ⁻ complex. In both cases, ligand L has bidentate coordination. Ligand L contacts with 3 and 5 M nitric acid to form adducts L·HNO₃ and L· (HNO₃)₂, respectively. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2460–2464, November, 2005.     

Titanium complexes bearing amine bis(phenolate) ligands: Synthesis,structure and catalysis in ring‐opening polymerization of lactide

Monomeric bis(isopropoxy) titanium complexes LTi(Oⁱ Pr)₂ (L =  ─ OC₆H₂–4‐R¹–6‐R²–2‐CH₂N[(CH₂)₂N(R³)₂]CH₂–4‐R⁴–6‐R⁵‐C₆H₂O ─ , R¹ = R² = ^t Bu, R³ = Et, R⁴ = R⁵ = Cl, (L¹)Ti(Oⁱ Pr)₂; R¹ = R² = Me, R³ = Et, R⁴ = R⁵ = Me, (L²)Ti(Oⁱ Pr)₂; R¹ = R² = ^t Bu, R³ = Et, R⁴ = OMe, R⁵ = ^t Bu, (L³)Ti(Oⁱ Pr)₂; R¹ = R⁴ = OMe, R³ = Et, R² = R⁵ = ^t Bu, (L⁴)Ti(Oⁱ Pr)₂; R¹ = R² = ^t Bu, R³ = Me, R⁴ = OMe, R⁵ = ^t Bu, (L⁵)Ti(Oⁱ Pr)₂) supported by amine bis(phenolate) ligands were synthesized and characterized using NMR spectroscopy and elemental analysis. The solid‐state structure of (L³)Ti(Oⁱ Pr)₂ was determined using single‐crystal X‐ray diffraction. (L^1–5)Ti(Oⁱ Pr)₂ were all found to initiate the ring‐opening polymerization of l ‐lactide and rac ‐lactide in a controlled manner at 110–160°C. As shown by kinetic studies, (L¹)Ti(Oⁱ Pr)₂ polymerized l ‐lactide faster than did (L^2–5)Ti(Oⁱ Pr)₂. In addition, good number‐average molecular weight and narrow polydispersity index (1.00–1.71) of polymers were also obtained. The microstructure of the polymers and a possible mechanism of coordination–insertion of polymerization were evidenced by MALDI‐TOF and ¹H NMR spectra of the polylactides.     

Synthesis and Electrochemistry of Soluble Phthalocyanine Complexes Containing Four Peripheral Dihexyl and Dihexylhexylmalonate Residues

Summary.  Tetrasubstituted phthalocyanines bearing four dihexylmalonate or dihexylhexylmalonate residues on the periphery (M[Pc(CH(COOC₆H₁₃)₂)₄] or M[Pc(C(COOC₆H₁₃)₂ C₆H₁₃)₄]; M = Pd(II), Cu(II), Co(II)) were synthesized from the anhydrous metal salts and the corresponding phthalonitriles. The complexes were only slightly soluble in polar solvents such as methanol and ethanol, but more soluble in less polar solvents such as benzene, toluene, and even hexane. The spectroscopic properties of the complexes were affected strongly by the electron withdrawing malonate units. Cyclic voltammetry on a platinum electrode in dichloromethane showed ligand-based one-electron transfers for Cu and Pd compounds, whereas the Co complex displayed metal-based or/and ligand-based one-electron transfers depending on the supporting electrolyte anion. The structures were confirmed by elemental analysis, ¹H NMR, ¹³C NMR, IR, mass (EI and FAB), and UV/Vis spectroscopy. Received November 24, 2000. Accepted (revised) January 2, 2001     

Palladium(II) complexes with R2edda-derived ligands. Part V. Reaction of O,O′-diethyl-(S,S)-ethylenediamine-N,N′-di-2-(3-methyl)butanoate with K2[PdCl4]

The reaction of K₂[PdCl₄] with [(S,S)-H₂(Et)₂eddv]Cl₂ diester (O,O′-diethyl-(S,S)-ethylenediamine-N,N′-di-2-(3-methyl)butanoate) (1) resulted in [PdCl₂{(S,S)-(Et)eddv-κ² N,N′,κO}] (2) complex with one hydrolyzed ester group. The compound was characterized by spectroscopic methods and it was found that the reaction is diastereoselective (¹H and ¹³C NMR; one diastereoisomer of four possible). In addition, the structure of 2 was confirmed by X-ray diffraction analysis, indicating that the product is the (R,R)–N,N′-configured isomer. DFT calculations support the formation of one diastereoisomer of 2.     

Oxidation of aryl vinyl sulfides in the ButOOH−Ti(OPri)4−(R,R)-diethyl tartrate system

Oxidation of aryl vinyl sulfides into aryl vinyl sulfoxides in the Bu¹OOH−Ti(OPrⁱ)₄−(R,R)-diethyl tartrate system was studied. The process afforded low optical yields (no more than 5%). A model of the oxidation was proposed that allows interpreting the dependence of the reaction enantioselectivity on the structure of a substrate. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1872–1873, September, 1998.     

Crystal Structure and Characterisation of Mercury(II) Dichromate(VI)

Summary. Dark-red single crystals of HgCr₂O₇ were grown by reacting HgO and CrO₃ in excess at 200°C for four days. The crystal structure (space group P3₂, Z = 3, a = 7.2389(10), c = 9.461(2) ?, 1363 structure factors, 57 parameters, R[F ²>2σ(F ²)] = 0.0369, wR(F ² all) = 0.0693) was determined from a crystal twinned by merohedry according to (110). It consists of nearly linear HgO₂ units ( (Hg–O) = 2.02 ?) and dichromate units that are linked into infinite chains ‘O₃Cr–O–CrO₃–Hg–O₃Cr–O–CrO₃’ running parallel to the c-axis. Six additional Hg–O contacts between 2.73 and 2.96 ? stabilise the structural arrangement. The dichromate anion exhibits a staggered conformation with a bent Cr–O–Cr bridging angle of 140.7(6)°. Upon heating above 300°C, HgCr₂O₇ decomposes in a two-step mechanism to Cr₂O₃. The title compound was additionally characterised by vibrational spectroscopy.